HP A6600 Configuration Manual page 78

WFQ queuing
Figure 26 WFQ queuing schematic diagram
Packets to be sent through
this port
WFQ is similar to WRR. They both support scheduling weights in queue length, and can work with SP
scheduling together. The difference is WRR enables you to set the maximum time a packet waits in queue, but
WFQ enables you to set the guaranteed bandwidth a WFQ queue can get during congestion.
CBQ
CBQ provides one FIFO queue for each user-defined class to buffer traffic of the class. When the network is
congested, CBQ classifies packets into user-defined classes, and assigns different classes of packets to
different queues after performing congestion avoidance and bandwidth restriction check. When dequeuing
packets, CBQ schedules packets from queues in proportion to their weights.
To ensure strict priority service for real-time traffic, CBQ provides LLQ queues. CBQ always schedules traffic
in LLQ queues preferentially. To guarantee that other queues can get served when congestion occurs, set the
maximum bandwidth for each LLQ queue. In normal cases, an LLQ queue can use more bandwidth than
allocated. When congestion occurs, the exceeding traffic is dropped. In addition, configure a burst size for
LLQ queues.
In addition, CBQ provides BQ and WFQ. The two types of queues use tail drop by default. Configure a
WRED drop policy to limit traffic.
The system matches packets against match criteria in the following order:
Against the classes in the order the class-behavior associations are configured.

Against the match criteria in the same class in the order they are configured.

Queue 1 Band width 1
Queue 2 Band width 2
......
Queue N-1 Band width N-1
Packet
classification
Queue N Band width N
Sent packets
Sending queue
Queue
scheduling
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Interface